The present invention relates to an apparatus for detecting a misfire in an internal combustion engine for a vehicle (hereinafter referred to simply as "engine").
Conventional detection of a misfire in an engine performed by a conventional detecting apparatus comprises the steps of detecting a rotational speed of the engine at least at two points in one ignition cycle, determining an amount of change in the rotational speed from the detected rotational speeds and determining whether a misfire has occurred by comparing the amount of change in the rotational speed of the engine or a result of statistic processing of the amount of change in the rotational speed with a misfire determination value obtained in accordance with an operating condition of the engine, since the rotational speed of the engine decreases when a misfire occurs (refer to JP-A-58-51243 and SAE 900232).